Emphasis will continue to be determination of the primary structure of human Tf. We expect to complete the structure of CNBr II-2 very soon. Since the structure of CNBr III is also available, we will concentrate on the large polypeptides constituting CNBr I. Most of the tryptic, chymotryptic, and peptic peptides have been sequenced. There still remains a major project of aligning these, however. A substantial effort will also be devoted to surveying mammalian cell lines for the ability to synthesize Tf. Primary candicates will be hepatoma cell lines and lines from mammary tumors. If we can identify a cell line that produces Tf, this will permit us to study the conditions under which Tf is synthesized and the factors involved in its regulation. Bibliographic references: H.E. Sutton and R.P. Wagner. 1975. Mutation and Enzyme Function in Humans. Annual Review of Genetic 9: 187-212.